This invention relates to industrial robots.
In recent years industrial robots have become relatively highly developed. For example in U.S. Pat. No. 3,661,051 granted May 9, 1972, hereby incorporated into the present application by this reference, a rotatable robot or programmed manipulator is disclosed which employs a continuously rotating memory drum in which may be stored signals representing a number of steps in a desired sequence of operations. A portable teach control assembly is employed during the teaching operation to establish a desired position of the manipulator arm which is then recorded on the memory drum. During repetitive work cycles, the recorded signals are used as command signals and are compared with encoder signals representing absolute position to move the manipulator arm to each set of positions in sequence. The manipulator arm may be moved over curved paths by employing artificial coincidence signals which are developed while large error signals still exist in the controlled axes. A common comparator and digital-to-analog converter is employed for all of the controlled axis which provides coincidence signals representing different magnitudes of error.
In U.S. Pat. No. 3,888,361, June 10, 1975, hereby incorporated into the present application by this reference a fixed base programmed manipulator arrangement is provided for cooperation with a continuously moving conveyor wherein the manipulator is positioned so that one axis such as the out-in-axis, is parallel to the conveyor. Synchronous operation with the conveyor while permitting limited lateral movements of the manipulator arm is achieved by employing a digital conveyor encoder as a source of continuously varying command signals for the out-in-axis of the manipulator. The arrangement does not require positioning of the conveyor at a large number of points along its path during the initial teaching mode of the manipulator apparatus.
In U.S. Pat. No. 3,525,382, Aug. 25, 1979, hereby incorporated into the present application by this reference, use of such a robot or programmable manipulator is disclosed for applicators in die casting and forging, and an infrared heat detector is utilized; and in U.S. Pat. No. 3,654,613 granted Apr. 4, 1972, the use of such a manipulator is specifically disclosed in connection with running hot billets from a furnace moving the billets into a press to be molded or stamped, and then remove the finished part from the press and place it in a receptacle. Moreover, in accordance with a further phase of the invention, the artificial end-of-program signal may be externally developed in response to a heat-sensing device, or other facility for sensing a characteristic of the part which is carried by the manipulator arm. If the desired characteristic is not detected by the sensing means, an artificial end-of-program signal is developed which causes the manipulator arm to be returned to its initial position without completing the entire program.
For example, one industrial robot is called an Unimate, trademark of Unimation, Inc. of Shelter Rock Lane, Derby, Conn. 06810. One model, the 4000B "is an industrial robot with a hydraulically powered arm having six programmed articulations and either a pneumatically-operated clamping/tooling device or a weld gun (usually called the "hand") at its outer end. A built-in digital memory system, in combination with an all solid-state electronic system, controls servo drives to move the arm-and-hand assembly through as many as six different basic types of movement. Three of these are arm motions: O: Out-in (radial extension or retraction); D: Down-up (vertical rotation); R: Rotary (waist rotation). The other three are motions of the wrist assembly. B: Bend (depression or elevation); Y: Yaw (rotation clockwise or counterclockwise); S: Swivel (rotation clockwise or counterclockwise). In each of the six motions, the prime moving force is generated by a hydraulic actuator under control of a servo valve. Hydraulic actuators for out-in and down-up motions are connected directly to their respective loads. For rotation, a rack and ring gear convert linear travel of pressure-balanced hydraulic pistons into rotary motion. A spring-loaded cylinder applies a constant engaging force to the rack to prevent backlash. Force generated by bend, swivel, and yaw actuators is transmitted by a system of chains, shafts, and gears to the respective loads. Since the wrist moves in and out with the arm, a ball-nut and spline-shaft arrangement provides means for transmitting power to these motions throughout the entire range of arm (boom) out-in motion. Bevel gears permit compact arm geometry. Hydraulic power for operation of the Unimate is provided by a complete self-contained hydraulic system." See Equipment Manual 398E1, May 1978, hereby incorporated into the present application by this reference.
However, even with all the sophisticated controls described in the above publications, it has been found that an industrial robot will occasionally abut an obstruction causing expensive damage and down time of the robot.
When the robot is fitted with a clamping or tooling device, it is frequently used to lift and place a work piece such as metal stock or formed articles in one or a series to desired stations and/or storing position.
The clamping or tooling device comprises a pair of laterally spaced outwardly exending fingers used to grasp a work piece. Preferably each finger includes a contoured claw at its outer end to aid in holding the work piece as it is transferred between stations.
The fingers are movable away from each other to place the work piece at a desired station.
The fingers extend outwardly from a gear box which allows 360.degree. of rotation of the fingers about a horizontal axis. Another gear allows at least 180.degree. of finger movement about a vertical axis. The fingers and supporting structure are also movable back and forth relative to the robot arm.